America’s deadliest pest on its way to eradication

AUSTIN – Birth control for insects? It worked in the late 1930s to eradicate a deadly agricultural pest called the screwworm, and it worked again in this century when the screwworm showed up in the Florida Keys.

The screwworm had not been seen in the United States for decades when it was found infesting endangered Key deer in 2016. The screwworm killed more than an eighth of the already miniscule Key deer population.

U.S. Department of Agriculture researchers John Welch and Pamela Phillips gave a session called “Dealing With Deadly Pests Through the Sterile Insect Technique”at the 2018 American Association for the Advancement of Science conference. They also discussed how the USDA partnered with the Panama Ministry of Agricultural Development to create a barrier zone to prevent re-infestation of the screwworm.

The Sterile Insect Technique was developed in the 1930s by entomologists Edward Knipling and Raymond Bushland. The technique exposes screwworm flies to low doses of atomic radiation, which makes them sterile – unable to reproduce. It is not genetic engineering, but autocidal control, which is altering the genome to control a species’ growth.

The sterile insect technique was first used to battle the screwworm in southern agricultural communities, and it has since has been used on other pests such as the Mediterranean fruit fly, the tsetse fly, and Aeges aegypti, the yellow fever mosquito.

Sterilizing screwworm flies has been the answer to infestation. Taking advantage of the pest’s own biology led scientists to discovering how to end sexual reproduction. The female screwworm mates only once in its short life span of three weeks. Sterilizing millions of flies, then releasing them to the infected area creates a mass decline in the population.

A screwworm larva up close. Photo by John Kucharskia.

The USDA has released 40 million flies into the Florida Keys. This technique is environmentally friendly and ethical, Welch said during the session.

Key deer population numbers have been affected not only by the screwworm, but by natural disasters. Data collected after Hurricane Irma showed that 14 to 22 percent of the deer population died in the storm. The average deer is only three feet tall and 95 pounds, the size of a dog.

Key deer numbers have fluctuated over time. Will the protection efforts help stabilize the population? Officials are now working on improving the rare species.